Bromide and Other Halide Ion Removal From Drinking Waters Using Silver-Amended Coagulation

High bromide ion concentrations are of concern because of formation of brominated disinfection byproducts in drinking water, which may be more toxic than their chlorinated analogs. Jar tests dosed with alum and silver were performed on several water samples with chloride-to-bromide (Cl:Br) ratios ranging from 15 to 866 mg Cl/mg Br. In lower-chloride waters (15 mg Cl/mg Br), silver-amended coagulation (SAC) removed 20–90% of the initial bromide. In higher-chloride water (525 mg Cl/mg Br), a silver dose of 15 mol Ag/mol Br achieved 40% bromide removal. Iodide and chloride removal also occurred during silver addition. SAC did not influence total organic carbon or turbidity removal, and residual silver was below the secondary maximum contaminant level but was successful in decreasing trihalomethane (THM) formation from 44 to 28 μg/L by shifting away from brominated THM species. SAC may only be applicable and cost-effective in a narrow range of waters with lower Cl:Br ratios, and other technologies should be developed for waters with >300 mg Cl/mg Br.